Neisseria gonorrhoeae Bacterial DNA Load in the Pharynges and Saliva of Men Who Have Sex with Men

Abstract

e Neisseria gonorrhoeae can be cultured in the saliva of individuals with pharyngeal gonorrhea. The aim of this study was to quantify the gonococcal bacterial DNA loads in the pharynges and saliva among men who have sex with men (MSM) with untreated pharyngeal gonorrhea. Untreated MSM who tested positive for pharyngeal gonorrhea by culture and returned for antibiotic treatment within 14 days at the Melbourne Sexual Health Centre between October 2014 and March 2015 were eligible for this study. The gonococcal bacterial DNA load was measured using real-time quantitative PCR. The median gonococcal bacterial DNA loads in the pharynges and saliva were calculated and compared to culture positivity using the Mann-Whitney U test. A total of 33 men were included in this study. The median gonococcal bacterial DNA load did not differ between the pharynges in men who were culture positive (2.5 ؋ 10 5 copies/swab) and culture negative (2.9 ؋ 10 4 copies/swab) (P ‫؍‬ 0.166) and the saliva (culture positive, 2.2 ؋ 10 5 copies/ml; culture negative, 2.7 ؋ 10 5 copies/ml) (P ‫؍‬ 0.499). The bacterial DNA load in the pharynges (P ‫؍‬ 0.695) and saliva (P ‫؍‬ 0.969) did not differ between who men returned for treatment within 7 days and those who returned 8 to 14 days later. Substantial gonococcal bacterial DNA loads were detected in both saliva and pharynges among MSM with pharyngeal gonorrhea. These findings suggest that gonorrhea can be transmitted via sexual practices involving exposure to saliva, such as oroanal practices (rimming) and saliva use as a lubricant for anal sex.T he high prevalence of gonococcal infection among men who have sex with men (MSM) is a public health issue in many developed countries (1-4). It is important to understand how gonorrhea is transmitted in order to effectively reduce the burden of this epidemic. An Australian-based mathematical model conducted by Hui et al. has shown that gonorrhea cannot be eliminated even if 100% condom use is practiced for anal sex among MSM (5), suggesting that gonorrhea has other routes of transmission other than penile-anal sex. Several observational studies have shown that kissing, oroanal (rimming) practices, oral-penile sex, and saliva use as a lubricant for anal sex are all associated with the detection of gonorrhea (6, 7). All of these sexual activities involve the use and transfer of saliva, indicating that saliva could potentially act as a vehicle for the transmission of gonorrhea during sex. There have been three published studies showing that gonorrhea can be cultured from saliva samples (8-10); however, none of these studies examined the gonococcal bacterial DNA load in saliva. If saliva can act as a medium for gonorrhea transmission, it is important to understand the relative concentrations of bacteria at different anatomical sites to provide further understanding on gonorrhea transmission. The aim of this study was to quantify the gonococcal bacterial DNA loads in saliva and the pharynx. MATERIALS AND METHODSThis cross-sectional study was conducted at the M...

Neisseria gonorrhoeaeDNA bacterial load in men with symptomatic and asymptomatic gonococcal urethritis

“…The results demonstrate that gonococcal load in the urethra is higher in men with urethral discharge on examination compared with asymptomatic men with no discharge: median 3.7×10 6 vs 2.0×10 5 copies per swab respectively. The results also suggest that gonococcal loads in men with urethral discharge are higher than loads seen in asymptomatic pharyngeal and rectal gonorrhoea infections in MSM in previous studies 3 4. Summarising previous inoculation studies of male urethral gonococcal infections using culture, Hobbs et al postulated the probability of infection may increase with the inoculum dose as measured by colony-forming units 2.…”

“…Men with symptoms suggestive of possible urethral gonorrhoea should thus be encouraged to present early for treatment to prevent further transmission. While men with asymptomatic urethral gonorrhoea had lower loads, these were comparable with those seen in pharyngeal infection 4. This suggests asymptomatic gonococcal urethral infection may also be potentially infectious and provides support for guidelines that recommend screening asymptomatic MSM for urethral gonorrhoea.…”

“…Furthermore, the median load in MSM with symptomatic gonococcal proctitis was 278 800 copies per swab, which was significantly higher than the median of 13 980 copies per swab among men with asymptomatic rectal gonorrhoea 3. In a more recent study of MSM attending our clinic, the median gonococcal load in PCR-positive pharyngeal infections was 248 512 copies per swab and 170 493 copies per swab in culture-positive and culture-negative men, respectively 4. The substantially higher pharyngeal loads in the second study likely reflect differences in study design and sampling.…”

“…In the first study by Bissessor et al , swabs were taken by clinicians during routine clinical care primarily from the tonsils only 3 12 13. In the second study by Chow et al, sampling was undertaken by clinicians trained to use a standardised method for collection from the tonsils and posterior oropharynx, and men had culture-positive pharyngeal gonorrhoea, which may have biased towards higher loads 3 4 14…”

“…If the bacterial load is a determinant of the transmissibility of gonorrhoea,2 then comparative bacterial loads from different anatomical sites of infection could provide an indication of the relative transmissibility of gonorrhoea from different sites. Previous studies have measured bacterial loads of N. gonorrhoeae in the pharynx and rectum of men but not the urethra 3 4…”